1. Field
Embodiments disclosed herein generally relate to a tunneling magnetoresistance (TMR) sensor for reading a recording from a magnetic recording medium using TMR, and in particular, to a magnetic cap of the TMR sensor.
2. Description of the Related Art
The heart of a computer is a magnetic disk drive which typically includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and/or write heads over a specific location on the rotating disk. The suspension arm biases the slider towards the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent a media facing surface (MFS), such as an air bearing surface (ABS), of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing, the write and read heads are employed for writing magnetic impressions to and reading magnetic signal fields from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
The read head typically utilizes a spin valve sensor, also referred to as a magnetoresistive sensor. One example of a magnetoresistive sensor is a TMR sensor. A TMR sensor may include a ferromagnetic layer, a pinned magnetic layer, a nonmagnetic coupling layer, a free magnetic layer, and a capping layer. In some cases, the capping layer is a multilayer structure separated from the free magnetic layer by a nonmagnetic spacer layer. The multilayer capping structure may comprise a ferromagnetic material layer and a nonmagnetic capping layer. The ferromagnetic material in the multilayer capping structure may diffuse through the nonmagnetic spacer layer into the free magnetic layer. Therefore, there is a need for an improved magnetoresistive sensor that prevents the ferromagnetic material layer of the capping structure from diffusing into the free magnetic layer of the sensor.